(1) Field of the Invention
This invention relates to footwear for preventing the wearer from being charged with static electricity, and it relates, in particular, to footwear used by people who work in or attend places wherein it is necessary to prevent the occurrence of problems caused by static electricity.
The problems caused by the static electricity can be classified into the following patterns.
1. Problems caused by electrostatic forces:
Faulty products due to the adsorption or repulsion of dust, various germs, etc., wrapping with cloth; clogging during sieving, etc.
Examples of the industries, etc., likely to be affected by these problems: the manufacture of medicines, foodstuffs, etc.; the manufacturing and assembling processes of precision machinery and tools, semiconductors, electronic components, photosensitive materials, etc.; the clean rooms of hospitals or other facilities wherein the air must be kept clean, etc.
2. Problems caused by electric discharges:
Electric shocks, ignition of inflammable materials, breakdown of IC elements, noise in electronic apparatuses, etc.
Examples of the industries, etc., likely to be affected by these problems: oil refining; the production and transportation of gases or other inflammables; tankers; gas stations; the electric power industry; the manufacture of electronic apparatuses, etc.
3. Problems caused by electrostatic fields:
Faulty operation of electronic apparatuses, breakdown of IC elements, formation of charged bodies due to electrostatic induction, etc.
Examples of the industries, etc., likely to be affected by these problems: the manufacture of semiconductors and electronic components; the maintenance of electronic apparatuses and computers, etc.
(2) Prior Art
Antistatic or conductive shoes are usually used in various work places to eliminate the static electricity with which a human body can be charged.
Antistatic shoes, which have an electrical resistance within the range of 1.0.times.10.sup.5 .OMEGA. to 1.0.times.10.sup.8 .OMEGA., fulfill the function of preventing the wearer from becoming charged with electricity due to faulty insulation of a distribution line or the like in the work place, i.e. the function of protecting the wearer from electric shocks, by leaking away the static electricity with which the human body can be charged. On the other hand, conductive shoes having a small electric resistance are used in places free from the danger of electric shocks. An example of such is illustrated in Japanese Industrial Standard JIS T 8103 (1983) entitled Anti-Electrostatic Footwears with/without Safety Toes.
Although enabling the removal of static electricity from the wearer charged therewith, these shoes have the fault that they can not prevent tiny pieces of human skin and dust such as waste fibers from falling onto the floor or into the air from the cuffs of the trousers worn by operators, etc. When overshoes covering the cuffs of the trousers are worn so as to compesate for this fault, the wearing of antistatic or conductive shoes becomes more troublesome because of these additional overshoes. In addition, there is the disadvantage that the antistatic or conductive shoes slip inside the overshoes which is uncomfortable for the wearer while walking. When overshoes alone are worn so as to avoid this discomfort, static electricity could not be eliminated safely, because the antistatic or conductive shoes are not worn.
(3) Brief Description of the Invention
The first object of the present invention is to furnish footwear which enables the safe leakage of static electricity from the wearer even when he is charged therewith, weakens electrostatic forces, prevents dust from being caught by clothes, checks any rise in potential and protects the wearer from electric shocks, in short, footwear which prevents the problems caused by static electricity and which can be used safely in the above industries, etc.
The second object of the present invention is to furnish footwear which has leg covers covering the cuffs of the trousers worn by operators, etc., so as to prevent dust from falling onto the floor or into the air from the cuffs.
The third object of the present invention is to furnish footwear constituted by antistatic or conductive shoes and leg covers connected thereto continuously, which enables the reduction of problems in wearing, compared with the practice in which overshoes are worn in addition to antistatic or conductive shoes, and which are comfortable in wear due to the constitution thereof enabling the elimination the disadvantage that antistatic or conductive shoes slip inside overshoes while the wearer thereof is walking.
The characteristics, principles and details of the present invention will be made more apparent by the following detailed description of the preferred embodiments of the present invention with reference to the attached drawings.